The present invention relates to a device for controlling a multi-cylinder internal combustion engine, in particular a diesel motor.
In a multi-cylinder internal combustion engine with a crank and a camshaft a control device computes when and how much fuel per cylinder must be injected. It must be guaranteed that the fuel is supplied to the individual cylinders at a proper time point and in a proper quantity. For performing computations in a correct way, the corresponding adjustment of the crank or camshaft of the internal combustion must be known. It is conventional to use corresponding sensors which scan the transmitter wheels provided with characteristic surfaces and connected with the shafts. By evaluations of the signals, the angular positions of the shafts can be determined.
In diesel internal combustion engines, for example in such which are based on distributor injection pumps, the measuring function is based on an accurate angle information, which is made available by an incremental angle sensor-system (IWZ system) for the metering control device. It is very important that the metering algorisms of the software can be synchronized to predetermined reference marks of the incremental tooth signals. For example the software uses as a reference a gap which is definitely provided on a transmitter wheel with uniform angle marks (teeth), which gap is formed by one or two missing angle marks. When inside an injection cycle, such a gap is not recognized or recognized too late, a synchronization error occurs.
In the currently utilized systems, actual synchronization errors are subjected to a so-called error repulsing routine. In other words, an error must occur continuously over a predetermined time period in order to be qualified as a defect classification. With the defect classification then the fuel metering is adjusted, since a correct function can no longer be guaranteed. Then a new synchronization of the software with the tooth signal, or in other words by evaluation of the intervals of signal flanks is performed. With such a process interruptions of the fuel metering are caused, which lead to interruptions in the ignition process, which in turn lead to affecting of the traveling comfort.
German document DE-OS 29 47 412 discloses a device for reference mark recognition in an internal combustion engine, in which the reference mark is formed as a gap between regular angle marks. The transmitter wheel is connected to the shaft of the internal combustion engine and sensed by a sensor. From the evaluation of the input signals of the sensor, the control device of the internal combustion engine can recognize the reference marks (gaps). In particular, first an evaluation is performed in which time intervals between predeterminable signal flanks are evaluated. When such a time distance is greater than a previously detected time distance, the reference mark is recognized. Subsequently, the next reference mark is recognized. In particular, a counter counts signal flanks upwards until a value which corresponds to the number of the angle marks between two reference marks. For controlling, at least it is checked timely whether the reference marks obtained by upward counting of the signal flanks correspond to the actual reference mark. For this purpose it is evaluated whether simultaneously to the recognized reference mark, the time distance between successive angle marks is greater than the predetermined time distances. If the both comparisons result in non-plausibility, the control device switches to a new synchronization, and the reference mark search is performed again exclusively after the time interval evaluation.